The Objectives of this study is to determine the effect(s) of daily non-caloric artificial sweetener (NAS) consumption (sucralose or aspartame) on the composition of the bacteria and also to determine the changes in glucose metabolism.

The trial will be 12 weeks randomized, cross-over and double blinded with 2 treatment intervention ( sucralose and aspartame) , there will be a run in period (4 weeks), then phase 1 treatment period for two weeks followed by four weeks washout period then phase 2 treatment period(2 weeks). Healthy, normglycemic (<5.6 mmol/L) males and females ( 17 total) of age 18-45 y with a body mass index (BMI) 20-25 kg/m2 will be recruited.

Each participants will be given the dose of sweetener aspartame or sucralose during the treatment phase in a double-blind procedure.

the participant will be asked to consume the sweetener in a mixed flavoured beverage during each visit in the treatment phase.

Blood and stool sample collection will take place before after the run-in period, and after the washout period, as well as after each two-week treatment period.

glucose measurement: Capillary blood will be collected during each visit by registered nurse. Blood will be collected at fasting and at 12,30,45,60,90 and 120 minutes after the participants drink a glucose drink (75g glucose) for Oral glucose tolerance test.

a food frequency questionnaire will be given to each participant in order to estimate how often each sweetener is consumed on a daily basis.

Participants will also be asked to complete weekly food diaries of food and drink consumption.

Inclusion Criteria:

• BMI between 20-25 kg/m2
• Fasting blood glucose (FBG) < 5.7 mmol/L
• women with regular menstrual cycle.

Exclusion Criteria:

• probiotic or antibiotic use within 6 months prior to the start of the study
• metabolic or gastrointestinal disorders (diabetes mellitus types 1 and 2, inflammatory bowel disease (IBD), irritable bowel syndrome (IBS), celiac disease, phenylketonuria)
• pregnant or lactating women